1. Field of the Invention
This invention relates to a new and improved shock absorber, and more particularly, to a new and improved shock absorber characterized generally by viscous damping as opposed to coulomb damping. The shock absorber of this invention may be used in substantially any application where viscous damping is required and under circumstances where hydraulic fluid leakage would be unsatisfactory or intolerble.
Because the basic damping stack or body lamination of this invention is made up of both leaf springs and viscoelastic sheets, the damping unit will always be characterized by a spring constant as well as a coefficient of viscous damping. Thus, a shock absorbing unit can be designed according to the teaching of this invention to resist large static and dynamic force and also to absorb, without damage, a large amount of dynamic energy in an impact situation. Hence the shock absorber is highly suitable for such applications as automobile bumpers. In such an application, the damping feature of the invention would permit a bumper to handle, without damage, higher vehicle speeds (just prior to impact) than could be sustained by any purely spring supported bumper. Furthermore, because of the spring leaf feature of the shock absorber the unit would be capable of handling ordinary vehicle pushing and nudging operations that are commonly encountered in the daily use of an automobile.
2. Description of the Prior Art
Heretofore, many attempts have been made to provide shock absorbers chiefly characterized by non coulomb damping. For example, the conventional shock absorbing devices used on automobiles and other vehicles are generally designed for use in cooperation with hydraulic fluid or air as the damping vehicle. Other areas of investigation have included such efforts as that disclosed in U.S. Pat. No. 3,809,420 to Peter A. Weller, which includes an energy absorbing bumper assembly having at least one elongated inner member and a pair of similarly elongated outer members which are disposed in parallel relationship to the inner member and on opposite sides thereof. The inner member is connected to each of the outer members by a plurality of spaced, parallel energy absorbing elements oriented at an acute angle with respect to the members being connected. The structure is, in effect, a plurality of parallelogram members and the individual cells of these members may be filled with an elastomeric material.
U.S. Pat. No. 2,661,943 to L. S. Wilbur discloses a similar cushioning device which includes a plurality of resilient metal layers spaced by alternate layers of a compressible material to form a shock absorber which will assume its original position when an applied load is removed. The layers of metal are formed with ribs or corregations designed to space the plates in the stack.
One of the disadvantages characteristic of non coulomb-type shock absorbers in current use is that of leakage of hydraulic fluid from the interior of the device. Not only does such leakage render the cushioning device inoperative, but the spilled hydraulic fluid frequently coats equipment and other machine parts and belts with a film which at best is difficult to remove, and at worst can be detrimental to the adjacent mechanisms. In the case of air actuated shock absorbers, rubber boots must be utilized to maintain a functional air pressure in the device, and such boots are subject to failure due to stress fatigue, oil or other liquid attack, and abrasion.
While the non coulomb shock absorbing devices such as those illustrated in U.S. Pat. Nos. 3,809,420 and 2,661,943 appear to be effective in absorbing the shock of loads of varying description, the disclosure in U.S. Pat. No. 3,809,420 is relatively complex and appears subject to permanent deformation, while the device illustrated in U.S. Pat. No. 2,661,943 appears to be chiefly applicable to absorption of static loads in a compression configuration.
Accordingly, it is an object of this invention to provide a shock absorber which is capable of damping both static and dynamic forces, including oscillating forces, in a flexure operation which approaches true viscous damping.
Another object of the invention is to provide a shock absorber which is characterized by alternate rectangular laminations of a viscoelastic material and leaf springs which operate by flexure between a pair of parallel end members to provide a shock absorbing function as the layers flex and the end members move in relative translation.
Yet another object of the invention is to provide a new and improved shock absorber which is characterized by layers of leaf spring having a spring constant and layers of a viscoelastic material having the approximate characteristics of viscous damping to permit the shock absorber to extend and compress in flexure rather than compression, and to return automatically to a neutral position when a given load is first applied and then removed.
A still further object of the invention is to provide an improved shock absorber which approaches true viscous damping, the end members of which undergo curvilinear translation and the alternate layers of viscoelastic material and spring steel of which undergo flexure as fixed end beams when the shock absorber is either compressed or extended by application of a load.
Another object of the invention is to provide a shock absorber which can be adjusted to damp substantially any given load by inserting or removing layers of either or both the viscoelastic material and the spring steel to provide a selected and appropriate shock absorbing function.
Yet another object of the invention is to provide a shock absorbing device which is capable of functioning both as a shock absorber and as a spring support for a vehicle or in other desired load support applications.
A still further object of the invention is to provide a shock absorber which is designed to extend and compress under load and to resume a neutral design configuration when unloaded.